High Energy Astrophysical Phenomena 12
☆ Lowest-mass X-ray selected AGNs in the Boötes Field
We present a multi-wavelength analysis of three candidate active galactic
nuclei (AGNs) in low-mass galaxies in the Bo\"otes field with the aim of
improving constraints on the occupation fraction of low-mass black holes (BHs).
Galaxies with low stellar masses ($M_{\star} < 10^{9.5} M_{\odot}$) are
particularly interesting hosts for AGNs as they may contain BHs that have not
grown significantly since the epoch of their formation in the early Universe.
Using archival data from the Chandra X-ray Observatory, we find three X-ray
luminous low-mass galaxies and assess whether they host AGNs. We find one of
these sources to be variable in the X-ray and compute its X-ray light curve and
spectrum. We compute the X-ray, mid-infrared, and [O III] luminosities and
compare them to established AGN luminosity relationships in the literature. We
then fit various star-forming, dust emission, and AGN templates to the spectral
energy distributions (SEDs). The star formation rates estimated from the SED
fits are unable to explain the observed X-ray luminosities of the candidates,
providing more support for the presence of AGNs. By analysing the deviation
from linear relationships between X-ray and mid-infrared luminosities, we find
these systems to be obscured (with $\log N_{\rm H}[{\rm {cm^{-2}}}] \sim 22.7,
> 25.0$, and $24.4$, respectively). We employ the scaling relationship between
BH mass and stellar velocity dispersion to estimate the BH masses as $\sim 10^5
- 10^6 M_{\odot}$ and accreting at Eddington ratios $10^{-2} < \lambda_{\rm
Edd} <10^{-1}$.
comment: Accepted for publication in MNRAS
☆ Evaluation of EAS directions based on TAIGA HiSCORE data using fully connected neural networks
A. P. Kryukov, S. P. Polyakov, Yu. Yu. Dubenskaya, E. O. Gres, E. B. Postnikov, P. A. Volchugov, D. P. Zhurov
The direction of extensive air showers can be used to determine the source of
gamma quanta and plays an important role in estimating the energy of the
primary particle. The data from an array of non-imaging Cherenkov detector
stations HiSCORE in the TAIGA experiment registering the number of
photoelectrons and detection time can be used to estimate the shower direction
with high accuracy. In this work, we use artificial neural networks trained on
Monte Carlo-simulated TAIGA HiSCORE data for gamma quanta to obtain shower
direction estimates. The neural networks are multilayer perceptrons with skip
connections using partial data from several HiSCORE stations as inputs;
composite estimates are derived from multiple individual estimates by the
neural networks. We apply a two-stage algorithm in which the direction
estimates obtained in the first stage are used to transform the input data and
refine the estimates. The mean error of the final estimates is less than 0.25
degrees. The approach will be used for multimodal analysis of the data from
several types of detectors used in the TAIGA experiment.
comment: The work was reported on the 8th International Conference on Deep
Learning in Computational Physics (DLCP2025), June 19-21, 2024, Moscow,
Russia (https://dlcp2024.sinp.msu.ru/). To bee published in Moscow University
Physics Bulletin
☆ Cross-Comparison of Sampling Algorithms for Pulse Profile Modeling of PSR J0740+6620
In the last few years, NICER data has enabled mass and radius inferences for
various pulsars, and thus shed light on the equation of state for dense nuclear
matter. This is achieved through a technique called pulse profile modeling. The
importance of the results necessitates careful validation and testing of the
robustness of the inference procedure. In this paper, we investigate the effect
of sampler choice for X-PSI (X-ray Pulse Simulation and Inference), an
open-source package for pulse profile modeling and Bayesian statistical
inference that has been used extensively for analysis of NICER data. We focus
on the specific case of the high-mass pulsar PSR J0740+6620. Using synthetic
data that mimics the most recently analyzed NICER and XMM-Newton data sets of
PSR J0740+6620, we evaluate the parameter recovery performance, convergence,
and computational cost for MultiNest's multimodal nested sampling algorithm and
UltraNest's slice nested sampling algorithm. We find that both samplers perform
reliably, producing accurate and unbiased parameter estimation results when
analyzing simulated data. We also investigate the consequences for inference
using the real data for PSR J0740+6620, finding that both samplers produce
consistent credible intervals.
comment: Submitted to PRD
☆ Neutrino Oscillation in Core Collapse Supernova: The Impact of Spacetime Geometry
Neutrino flavor evolution inside a core-collapse supernova is a topic of
active research. The core of a supernova is an intense source of neutrinos and
antineutrinos. Self-interaction among neutrinos (as well as antineutrinos)
gives rise to a rich phenomenology not seen in terrestrial situations. In
studies of the dynamics of flavor evolution in such environments, the
gravitational effects are generally ignored. Although the curvature outside a
dense core does not deviate much from a flat space, the spin of the neutrinos
can still couple to the torsion of the spacetime. These extra degrees of
freedom of curved spacetime have interaction strengths that are proportional to
the density of the neutrinos and the other fermions \cite{Chakrabarty:2019cau}
\cite{Barick:2023qjq} as well as the coupling constants of the spin-torsion
interaction. We have studied the effects of such interactions in flavor
evolution inside a core-collapse supernova \cite{Ghose:Manuscript}. The
self-interaction gets modified by the spin-torsion interaction and the
oscillation dynamics is modified. We have seen that there are noticeable
changes in the flavor dynamics when the neutrino density is uniform. We have
also studied the effects of such interaction in a realistic core-collapse
supernova (CCSN). As neutrino astronomy enters the precision era, this study
will shed light on the potential of neutrino fluxes from CCSN to probe the
neutrino-neutrino interaction.
comment: Presented by Indrajit Ghose at the XXVI DAE-BRNS HEP Symposium, 19-23
Dec 2024, Varanasi
☆ Radio observations of the ultra-long GRB 220627A reveal a hot cocoon supporting the blue supergiant progenitor scenario
James K. Leung, Om Sharan Salafia, Cristiana Spingola, Giancarlo Ghirlanda, Stefano Giarratana, Marcello Giroletti, Cormac Reynolds, Ziteng Wang, Tao An, Adam Deller, Maria R. Drout, David L. Kaplan, Emil Lenc, Tara Murphy, Miguel Perez-Torres, Lauren Rhodes
We present the discovery of the radio afterglow of the most distant
ultra-long gamma-ray burst (GRB) detected to date, GRB~220627A at redshift
$z=3.084$. Its prompt gamma-ray light curve shows a double-pulse profile, with
the pulses separated by a period of quiescence lasting ${\sim} 15\,$min,
leading to early speculation it could be a strongly gravitationally lensed GRB.
However, our analysis of the $\textit{Fermi}$/GBM spectra taken during the time
intervals of both pulses show clear differences in their spectral energy
distributions, disfavouring the lensing scenario. We observed the radio
afterglow from $7$ to $456\,$d post-burst: an initial, steep decay ($F_{\nu}
\propto t^{-2}$) is followed by a shallower decline ($F_{\nu} \propto
t^{-1/2}$) after ${\sim} 20\,$d. Our afterglow modelling shows that these radio
properties can be explained by the presence of a slow, wide ejecta component in
addition to a fast, narrow ejecta component, consistent with the picture of a
highly-collimated jet and its thermal cocoon decelerating into the ambient
medium. The properties of the cocoon point toward a progenitor with a large
stellar radius, supporting the blue supergiant scenario proposed for ultra-long
GRBs. We also conducted an independent test of the lensing hypothesis via Very
Long Baseline Interferometry (VLBI) observations at ${\sim} 12\,$d post-burst
by searching, for the first time, for multiple images of the candidate lensed
GRB afterglow. Our experiment highlighted the growing need for developments in
real-time correlation capabilities for time-critical VLBI experiments,
particularly as we advance towards the SKA and ngVLA era of radio astronomy.
comment: 19 pages, 7 figures; submitted to ApJ, comments are welcome
♻ ☆ On testing in-vacuo dispersion with the most energetic neutrinos: KM3-230213A case study
Giovanni Amelino-Camelia, Giacomo D'Amico, Giuseppe Fabiano, Domenico Frattulillo, Giulia Gubitosi, Alessandro Moia, Giacomo Rosati
The phenomenology of in-vacuo dispersion, an effect such that quantum
properties of spacetime slow down particles proportionally to their energies,
has been a very active research area since the advent of the Fermi telescope.
One of the assumptions made in this 15-year effort is that the phenomenology of
in-vacuo dispersion has a particle-energy sweet spot: the energy of the
particle should be large enough to render the analysis immune to
source-intrinsic confounding effects but still small enough to facilitate the
identification of the source of the particle. We use the gigantic energy of
KM3-230213A as an opportunity to challenge this expectation. For a neutrino of
a few hundred PeVs a transient source could have been observed at lower
energies several years earlier, even assuming the characteristic scale of
in-vacuo dispersion to be close to the Planck scale. We report that GRB090401B
is in excellent directional agreement with KM3-230213A, and we discuss a
strategy of in-vacuo-dispersion analysis suitable for estimating the
significance of KM3-230213A as a GRB090401B-neutrino candidate. The p-value
resulting from our analysis (0.015) is not small enough to warrant any
excitement, but small enough to establish the point that a handful of such
coincidences would be sufficient to meaningfully test in-vacuo dispersion.
comment: V2 differs from V1 mainly because of an improved version of our
indicator S_E, producing minor quantitative changes (but it could impact more
significantly future similar studies)
♻ ☆ Ultra-high-energy event KM3-230213A constraints on Lorentz Invariance Violation in neutrino sector
We discuss the constraints on superluminal neutrino Lorentz Invariance
Violation (LIV) parameters from the observation of the ultra-high-energy event
KM3-230213A by KM3NeT collaboration in cases of linear $n=1$ and quadratic
$n=2$ LIV scenarios. Assuming extragalactic origin of the event, we obtain the
constraints on LIV mass scale $\Lambda_{n=1} = 5.4 \times 10^{30}\, \mbox{GeV}$
and $\Lambda_{n=2} = 3.5 \times 10^{19}\, \mbox{GeV}$ from the absence of
neutrino splitting.
comment: 3 pages, v2: Refs added, typos corrected
♻ ☆ SpectrAx: Spectral Search of Axion-Like Particles Using Multi-Band Observations of Galaxy Clusters from SKA, SO, CMB-S4 and eROSITA
The existence of axions or Axion-Like Particles (ALPs) has been predicted by
various Beyond Standard Model (BSM) theories, and the proposed photon-ALP
interaction is one of the ways to probe them. Such an interaction will lead to
photon-ALP resonant conversion in galaxy clusters, resulting in a polarized
spectral distortion in the CMB along the cluster line of sight. The estimation
of this signal from galaxy clusters requires an estimation of their electron
density and magnetic field profiles, as well as their redshifts. We have
developed a new Bayesian framework \texttt{SpectrAx} that can use observations
from different electromagnetic bands such as radio, CMB, optical, and X-ray to
infer the astrophysical properties of a galaxy cluster, such as cluster its
redshift, electron density and magnetic field, along with the BSM physics such
as ALPs. We use simulated redshifts in our analysis, but that can be obtained
by cross-matching with optical surveys having overlapping sky regions with the
galaxy clusters. Also, we use radial profiles that are motivated from
observations of galaxy clusters at low redshifts. By using the simulated data
corresponding to the ALP mass of $10^{-14}$ eV for upcoming CMB surveys such as
Simons Observatory (SO) and CMB-S4 in combination with Square Kilometer Array
(SKA) and extended ROentgen Survey with an Imaging Telescope Array (eROSITA) we
demonstrate the capability in accurately inferring the ALPs coupling strength
along with the radial profile of electron density and magnetic field from
galaxy clusters. The application of this framework to the data from future
surveys by combining SKA+SO+eROSITA and SKA+CMB-S4+eROSITA will make it
possible for the first time to explore both astrophysics and BSM physics from
low-redshift galaxy clusters using a multi-band approach.
comment: 35 pages, 12 figures, 6 tables, Published in JCAP
♻ ☆ On the Feasibility of Deriving Pseudo-Redshifts of Gamma-ray Bursts from Two Phenomenological Correlations
Accurate knowledge of gamma-ray burst (GRB) redshifts is essential for
studying their intrinsic properties and exploring their potential application
in cosmology. Currently, only a small fraction of GRBs have independent
redshift measurements, primarily due to the need of rapid follow-up optical/IR
spectroscopic observations. For this reason, many have utilized
phenomenological correlations to derive pseudo-redshifts of GRBs with no
redshift measurement. In this work, we explore the feasibility of analytically
deriving pseudo-redshifts directly from the Amati and Yonetoku relations. We
simulate populations of GRBs that (i) fall perfectly on the phenomenological
correlation track, and (ii) include intrinsic scatter matching observations.
Our findings indicate that, in the case of the Amati relation , the
mathematical formulation is ill-behaved so that it yields two solutions within
a reasonable redshift range $z \in [0.1, 10] $. When realistic scatter is
included, it may result in no solution, or the redshift error range is
excessively large. In the case of the Yonetoku relation, while it can result in
a unique solution in most cases, the large systematic errors of the redshift
calls for attention, especially when attempting to use pseudo redshifts to
study GRB population properties.
comment: Accepted for publication in ApJ
♻ ☆ Chiral Symmetry in Dense Matter with Meson Condensation
Kaon condensation in hyperon-mixed matter [($Y$+$K$) phase], which may be
realized in neutron stars, is discussed on the basis of chiral symmetry. With
the use of the effective chiral Lagrangian for kaon--baryon and kaon--kaon
interactions; coupled with the relativistic mean field theory and universal
three-baryon repulsive interaction, we clarify the effects of the $s$-wave
kaon--baryon scalar interaction simulated by the kaon--baryon sigma terms and
vector interaction (Tomozawa--Weinberg term) on kaon properties in
hyperon-mixed matter, the onset density of kaon condensation, and the equation
of state with the ($Y$+$K$) phase. In particular, the quark condensates in the
($Y$+$K$) phase are obtained, and their relevance to chiral symmetry
restoration is discussed.
comment: 22 pages, 7 figures, published in Symmetry 2025,17,270, the Special
Issue: Chiral Symmetry, and Restoration in Nuclear Dense Matter. arXiv admin
note: substantial text overlap with arXiv:2411.09967
♻ ☆ Discovery of high-frequency quasi-periodic oscillation in short-duration gamma-ray bursts
Rapidly rotating newborn magnetars, which originate from binary neutron star
(NS) mergers and serve as the central engines of short gamma-ray bursts (GRBs),
may leave some imprints on their prompt gamma-ray light curves even though they
are far from their radiating fireballs. A high-frequency quasi-periodic
oscillation (QPO) would be a unique feature for the magnetar central engine,
especially a hypermassive magnetar. By conducting a systematic analysis of the
prompt gamma-ray light curves from 605 short GRBs observed by {\em
Fermi}/Gamma-ray Burst Monitor, we have identified such QPO signals in three
GRBs (e.g. GRB 120323A, GRB 181222B, and GRB 190606A). The QPOs that peaked at
$1258^{+6}_{-6}$ Hz for GRB 120323A, $623^{+4}_{-4}$ Hz for GRB 181222B, and
$1410^{+4}_{-5}$ Hz for GRB 190606A are all with a confidence level above 5.2
$\sigma$. The high-frequency QPO signals of those three short GRBs may be
caused by a hypermassive magnetar acting as the central engine in a binary NS
merger of a binary NS.
comment: 11 pages, 1 Table, 7 Figures, accepted for publication in MNRAS, and
matched with the published verison
♻ ☆ Exploring Axion-Like Particle from observation of FSRQ Ton 599 by Fermi-LAT
High energy photons traveling through astrophysical magnetic fields have the
potential to undergo oscillations with axion-like particles (ALPs), resulting
in modifications to the observed photon spectrum. High energy $\gamma-$ray
sources with significant magnetic field strengths provide an ideal setting to
investigate this phenomenon. Ton 599, a flat spectrum radio quasar with a
magnetic field strength on the order of Gauss in its emission region, presents
a promising opportunity for studying ALP-photon oscillations. In this study, we
analyze the effects of ALP-photon oscillations on the $\gamma$-ray spectrum of
Ton 599 as observed by Fermi-LAT. Our investigation considers the potential
influences of the broad-line region and dusty torus on the $\gamma-$ray
spectrum of Ton 599. We set the constraints on the ALP parameters at the $95\%$
confidence level, and find that the constraints on \(g_{a\gamma}\) can reach
approximately \(2 \times 10^{-12}~\mathrm{GeV}^{-1}\) for \(m_a \sim
10^{9}~\mathrm{eV}\).